Parts such as the Gasket Kit A: Gasket,tensioner (mca), Washer Seal, 6mm, Gasket,cylinder H (nas), Parking,tappet Co (nas) are included in the Trx300 Fourtrax 1990 (l) Australia Gasket Kit A parts fiche.
In this schematic the "Washer Seal 8mm" is used most often.
The Trx300 Fourtrax 1990 (l) Australia Gasket Kit A consists of fourteen pieces with the Gasket Kit A (mca) being the most expensive.